Other cylinders to prevent a recurrence, since it is possibleįor a small object to "travel" from one cylinder toĪnother where a large degree of valve overlap exists. When this condition is discovered, check the Remove the foreign object from the engine and/or install the correct reach plug. Causes a dead cylinder and could result in piston damage. May be caused by a foreign object in the combustion chamber or the piston striking an incorrect reach (too long) plug. Surface of the ground electrode to become thinner and the tip of the electrode will look as if it has been chipped. Lead Erosion - Caused by lead compounds in the gasoline which react chemically with the material of the electrodes at high temperatures. The surface of the electrodes are also fretted and rough.Ībnormal Erosion - Caused by the effects of corrosion, oxidation, reaction with lead, all resulting in abnormal gap growth. Oxidation - The material of the electrodes has oxidized, and when oxidation is heavy Use care when setting the gaps on new plugs. Make sure the fuel antiknock values meet engine requirements. Mixtures, and insufficient octane rating of the gasoline. The explosion that occurs in this situationĪpples extreme pressures on internal engine components.Ĭauses include ignition time advanced too far, lean air/fuel Improper gap setting techniques can also result in a fractured insulator tip. Consider using a colder plug is driving habits warrant. Normal deposits melt to form a conductive coating which can causes misfiring at high speeds. Indicates that combustion chamber temperatures have risen suddenly during hard acceleration. Insulator has yellowish, glazed appearance. Too high for the engine or its operating conditions. Induction between spark plug wires), or the plug heat range is It may originate from glowingĬombustion chamber deposits, hot spots in the combustion chamberĭue to poor control of engine heat, cross-firing (electrical One or a combination of several engine operating conditions are Can lead to engine damage.Ĭheck for the correct plug heat range, over advanced timing ignition, lean fuel mixture, insufficient engine cooling and lack of lubrication. Insulators are white, but may be dirty due to misfiring or flying debris in the combustion chamber. Usually, the electrode surface is rather lustrous and uneven. When theseĬonditions prevail, even a plug of the correct heat range will System efficiency (scale, stoppages, low level), a very leanĪir/fuel mixture, or a leaking intake manifold. Results in shortened plug life.Ĭaused by over advanced ignition, timing, poor engine cooling Lubricating Oil - Carbon, Calcium, Sulphur, Barium, Zincīlistered, white insulator, eroded electrode and absence of deposits.The accumulation of deposits is influenced by oil leakage, fuel quality and the engine's operating period. These materials shed from the piston crown or valve heads, andĪre thrown against the hot insulator surface. Insulator and often occurs after a long delayed tune-up.īy-products of combustion may loosen suddenly. These can be detected by a resistance tester at room temperature.Īs "spotted" deposits on the firing tip of the Lead Fouled - Lead fouling usually appears as yellowish brown deposits on the insulator nose. Causes hard starting, misfiring and hesitation Oil is leaking past worn valve guides or piston rings into the combustion chamber. Oil Fouled - Oily coating caused by poor oil control. Excessive amounts may mask the spark, causing misfiring and hesitation during acceleration. Causes misfiring, hard starting and hesitation.Īsh Fouled - Light brown deposits encrusted on the side or center electrodes or both. Performance and a loss in fuel economy are traits of a wornĬarbon Fouled - Dry sooty deposits indicate and rich mixture or weak ignition. Occur when the engine is quickly accelerated. Higher voltage requirements, as much as 100% above normal, may
Will continue to increase with additional miles of travel. Voltage required to fire the plug has approximately doubled and Normal color.Ĭauses hard starting in damp or cold weather and poor fuel economy. Rounded electrodes with a small amount of deposits on the firing end. When new spark plugs are installed, replace with plugs of the same heat range. Correct heat range for engine and operating conditions. Brown to grayish-tan color and slight electrode wear.